The fifth generation (5G) wireless system will comprise Long Term Evolution (LTE) together with a new radio-access technology, which is denoted by “NX” (next generation) in the following. LTE will focus on backwards-compatible enhancements in existing spectrum, while NX will focus on new spectrum, i.e. spectrum where LTE is not deployed.
NX will run over even higher frequencies than current systems due to lack of low frequency resources and the coverage provided by radio access points (APs) will be smaller than the coverage provided by existing nodes, such as 3G Node B and 4G eNodeB. With small AP coverage, comprising e.g. beam sectors, the mobility robustness is of critical importance in order to keep the user satisfaction high. A user traveling fast between different small coverage areas, e.g. moving between different beams, should still obtain uninterrupted service in order to maintain the user satisfaction. This requires careful consideration in view of mobility issues, such as handover.